Aspartate-specific cysteine proteases (ASCPs) play a central and evolutionarily conserved role in transducing the apoptotic signal and final execution of apoptosis (Martin, S. J. et al., Cell 1995, 82, 349-352; Henkart, P. A., Immunity 1996, 4, 195-201; Takahashi, A. et al., Curr. Opin. Gen. Dev. 1996, 6, 50-55; Fraser, A. et al., Cell 1996, 85, 781-784; and Alnemri, E. S., J. Cell. Biochem. 1996, 62, In Press). In the human there are ten different ASCPs, divided into three subfamilies based on their homology to the mammalian proinflammatory prototype interleukin 1-beta converting enzyme (ICE) and the nematode proapoptotic prototype CED-3 (Fernandes-Alnemri T. et al., Proc. Natl. Acad. Sci. 1996, 93, 7464-7469; and Srinivasula, S. M., et al., J. Biol. Chem. 1996, 271, In Press). In mammalian cells it is now believed that the two ASCPs, Mch4 and Mch5 (MACH/FLICE), which contain two FADD-like domains in their long N-terminal prodomain might be the most upstream transducers of diverse apoptotic signals, whereas CPP32, Mch2, and Mch3 which have short prodomains are the downstream executioners of apoptosis (Fernandes-Alnemri, T. et al., Supra; Srinivasula, S. M., et al., Supra; Boldin, M. P. et al., Cell 1996, 85, 803-815; and Muzio, M. et al., Cell 1996, 85, 817-827).
Studies with the baculovirus Autographa californica and its insect host S. frugiperda identified baculovirus encoded proteins, p35 and IAPs, that suppress baculovirus-induced apoptosis in S. frugiperda cells (Clem, R. J. et al., Science 1991, 254, 1388-1390; Crook, N. E. et al., J. Virol. 1993, 67, 2521-2528; and Birnbaum, M. J. et al., J. Virol. 1994, 68, 2521-2528). These proteins are expressed by the baculovirus to counter the host's antiviral defense (i.e., apoptosis) to ensure virus latency and multiplication. Mammalian antiapoptotic proteins homologous to baculovirus IAPs have recently been identified (Rothe, M. et al., Cell 1995, 83, 1243-1252; Liston, P. et al., Nature 1996, 379, 349-353; and Uren, A. G. et al., Proc. Natl. Acad. Sci. USA 1996, 93, 4974-4978). In contrast, no mammalian counterpart of p35 has yet been identified. Nevertheless, p35 is an effective suppressor of apoptosis in mammalian cells (Rabizadeh, S. et al., J. Neurochem. 1994, 61(6), 2318-2321; Martinou, I. et al., J. Cell Biol. 1995, 128, 201-208; and Beidler, D. R. et al., J. Biol. Chem. 1995, 270, 16526-16528). Its anti-apoptotic activity is attributed to its ability to interact with and potently inhibit members of the ASCP family (Bump, N. J. et al., Science 1995, 269, 1885-1888; and Xue, D et al., Nature 1995, 377, 248-251). This suggests that the apoptotic program in S. frugiperda is similar to the mammalian program and is mediated by active ASCP(s). This is further supported by the recent observation that baculovirus infection of S. frugiperda cells activate an ASCP that can cleave p35 (Bertin, J. et al., J. Virol. 1996, 70, 6251-6259).
There is a need to identify and clone the S. frugiperda ASCP that is responsible for execution of apoptosis in this organism. There is a need to identify proteases, particularly those involved in apoptosis. There is a need to identify compounds that inhibit proteases. There is a need to identify compounds that enhance the activity of proteases. There is a need to study and understand the mechanisms by which apoptosis is initiated, proceeds and is inhibited, and for reagents useful in such studies. There remains a need to identify new protease inhibitors and drugs for preventing or initiating apoptosis. There is a need for kits and methods of identifying such compounds. There remains a need to identify new protease activity enhancers and drugs for preventing or initiating apoptosis. There is a need for kits and methods of identifying such compounds. There is a need for isolated proteases and for compositions and methods of producing and isolating proteases. There is a need to isolated proteins that are proteases. There is a need to isolated nucleic acid molecules that encode proteases.